Corrosion inhibitor



Patented Oct. 11, 1949 CORROSION INHIBITOR Edward A. Bried, Newport, Del., assignor to Hercules Powder Company, Wilmington, Del., a.

corporation of Delaware No Drawing. Application December 31, 1946, Serial No. 719,615

2 Claims.

This invention relates to the protection of metal surfaces and more particularly iron and steel surfaces against corrosion. More particularly, it relates to corrosion inhibitors, the active ingredient of which is an amine of a rosin or a salt thereof.

Metal surfaces of tools, articles of manufacture and machinery which are exposed to weather, and other surfaces which are exposed to dilute acids and moisture such as the moving parts of internal combustion engines require the use of an inhibitor to prevent rusting and corrosion of the surfaces. This is especially true for iron or steel surfaces. Corrosion inhibiting compositions containing amines have been used in the past to protect these metal surfaces. These compositions have not been entirely satisfactory, however, due to deficiencies in one or more of the following desired characteristics: (1) Oil wettability of metal surfaces, (2) adhes'iveness to metal surfaces, (3) chemical stability, (4) low volatility, (5) water insolubility and repellancy.

Now in accordance with this invention, it has been found that metal surfaces may be inhibited against corrosion by coating the metal surfaces with a thin film of an amine of a stabilized rosin or an oil-soluble salt thereof. The amine or its salt may be applied as a solution thereof in a volatile solvent or it may be applied as a constituent of a composition containing an unctuous solvent. There are thus provided compositions which are superior in preventing corrosion due to their good preferential wetting of metal and their adhesion to the metal and their ability to repel water. The compositions are effective over long periods of time because of their low volatility, stability, water insolubility and resistance to washing away when exposed to water.

The following examples are illustrative ofthe effectiveness of stabilized rosin amines and oilsoluble salts thereof as corrosion inhibitors.

I Ewamp le I genalted rosin amine naphthenate, prepared by melting naphthenic acid, molecular weight 232, with the rosin amine, was substituted for the stearate in the lubricating oil. Steel and iron panels dipped in 0.15% aqueous HBr solution and then in the same oil containing no inhibitor taken as blanks rusted badly in one hour when exposed to similar atmospheric conditions.

Emample II amine naphthenate'showed very little rusting.

compared with a control panel'which was not treated with a rosin amine or rosin aminesalt solution.

Example III Iron nails (20 penny-4 inches long) were treated as in Example II and tested by partial immersion in sea water for 90 hours at 25 C.

Very little rusting of the treated nails was evident in comparison with the control.

Example IV treated panels along with untreated panels were then exposed in a humidity cabinet at relative humidity at F. for ten days. The treated panels were still bright and shiny while the control was completely rusted.

Example V Freshly sanded steel panels (1020 S. A. E.) were coated with a thin uniform coating of about five mil thickness of petrolatum containing 1% of dehydrogenated rosin amine and exposed to outdoor weather for 22 days. Similar panels coated with petrolatum containing 1% dehydrogenated rosin amine in the form of the stearate and the naphthenate and an uncoated panel as a control were exposed to outdoor weather at the same time. After 22 days the panels coated with the inhibitor compositions were still bright and shiny while the control coated with petro- 3 latum containing no inhibitor was speckled with rust spots.

Similar panels coated with petrolatum containing hydrogenated rosin amine, hydrogenated rosin amine laurate and hydrogenated rosin amine naphthenate showed similar rust inhibiting characteristics on outdoor exposure.

The stabilized rosin amines which may be used alone or in the form of its salts as a corrosion inhibiting base in accordancewith this invention are dehydrogenated rosin amine, disproportion- .ated rosin amine, and hydrogenated rosin amine.

Th deh drogenated rosin amine and its salts are particularly eiiective due to their greater chemical stability over long periods of time. The rosin amines may be used in the form of the free amine or in the form of an oil-soluble salt which is resinous, waxy, or balsamlike in nature.

The rosin amine salts which are eifective corrosion inhibitors are the salts of saturated fatty acids and naphthenic acids having a molecular weight within the range of about 170-350. Particularly effective are the rosin amine salts of lauric, stearic, and coconut oil fatty acids and naphthenic acids of molecular weight within the range of about 170-280.

The rosin amines used for inhibiting corrosion may be prepared from dehydrogenated rosin, disproportionated rosin or hydrogenated rosin by first reacting with ammonia to form the nitrile and then hydrogenating the nitrile to the amine' The step of making the nitrile may be carried out by passing gaseous ammonia into the molten ros n material and vaporizing the water as fast as it is formed or by heating the rosin material and ammonia in the presence of a dehydration catalyst. The nitrile is preferably purified b alkali extraction or by distillation to remove unconverted acids prior to hydrogenation to the amine, since the acidic materials frequently destroy the activity of the hydrogenation catalyst. The hydrogenation of the nitrile may be carried out in the presence or absence of a solvent and in the presence or absence of ammonia. The catalyst may be any of the well-known hydrogenation catalysts such as Raney nickel, Raney cobalt,-act1- vated nickel, cobalt, palladium or platinum, etc., and supports may be used if desired. Th hydrogenation is usually carried out under a pressure of about 200 to about 8,000 pounds per square in at a temperature of about 20 C. to about 200 C.

The stabilized rosin amines and their salts may be applied to metal surfaces to be protected as a solution in a volatile solvent or they may be used in conjunction with an unctuous solvent with or without a volatile solvent. The rust inhibiting composition may be applied either by spraying, dipping, or brushing, and the application can be made either hot or cold, depending upon the fluidity of the composition. When volatile solvents are used, hydrocarbon solvents such as kerosene, naphtha, mineral spirits, benzene, toluene, etc., or chlorinated hydrocarbon solvents such as carbon tetrachloride, ethylene chloride, etc., are preferred. The amount of volatile solvent used may vary from none at all to about 100 times the weight of the rosin amine material when the rosin amine material is the only nonvolatile component. The stabilized rosin amines and salts of this invention are viscous balsamlike to waxlike materials which adhere tenaciously to metal surfaces and do, not require an added component to act as a fixative. certain uses to use It is convenient, however, for an unctuous solvent with the rosin amine base. When an unctuous solvent is used, the unctuous solvent may include as a major component lubricating oil, mineral oil, grease, lard, rosin oil, paraffin waxes, petrolatum, vaseline, vegetable oils, lanolin, fats, and waxes. The unctuous solvent should be saturated or nonoxidizing and nondrying in character. Volatile solvents may also be used in an amount preferably not greater than about ten times the-weight of unctuous solvent when an unctuous solvent is used. In a satisfactory corrosion inhibiting composition, as little as 0.5% of the resin amine or its salt based on the weight of unctuous solvent may be present. It is preferred, however, to use about 1-5% rosin amine material as the corrosion inhibiting base in the unctuous solvent material.

The thickness of the film of the stabilized rosin amine materials for adequate protection should from about 0.02 to about 5.0 mils. A film of about 0.05 mil thickness is deposited on a panel dipped in a 1% xylene solution of dehydrogenated rosin amine and the solvent evaporated. A film base oil or grease.

of about 0.6 mil thickness is obtained by dipping a steel panel into S. A. E. lubricating oil containing 1% disproportionated rosin amine stearate dissolved therein andallowing to drain at room temperature. A film of 5 mil thickness may be obtained by brushing a heavy oil or grease containing a minor portion of the stabilized rosin amine or its stearate or naphthenate.

The metal surfaces to be protected by the compositions 'of this invention may, if desired, be given any pretreatment known in the art such as sanding, polishing, pickling, treatment with chromic acid, oxalic acid, ferrous dihydrugen phosphate, phosphoric acid or washing, scrubbing, and the like. On the other hand, pretreatment may be omitted, if desired.

The compositions of this invention may be used for the protection of any metal surfaces which corrode on exposure to moisture and corrosive acids in the atmosphere, or the metal surfaces of internal combustion engines, cylinders of steam engines, articles of manufacture such as nails, screws and other hardware, tools, instruments, implements, farm equipment such as plows, mowers, etc. The compositions are most effective on' iron or steel surfaces.

The rosin amines and their higher fatty acid salts and naphthenic acid salts are particularly effective as corrosion preventives because of their stickiness which enhances their adhesiveness to metals and makes them effective even without a They are especially effective in flowing evenly on metal-surfaces because of their wetting action on the metal surfaces and they are effective over long periods because of their chemical stability and low volatilit and because they are water-repellant and are not washed away by water.

I By the term stabilized rosin amine a rosin amine having the ring structure bilized rosin acid such as dehydroabietic hydroabietic acid, or tetrahydroabietic mixture of such rosin amines. The term "disproportionated rosin amine is intended to cover a mixture which is chiefly dehydroand dihydrorosin amines.

What I claim and is meant of a staacid, diacid or a desire to protect by Letters Patent is:

siolvent. otda cogosion inhibiting salt at; dteizy- REFERENCES CITED ogenate ros amine and a satura a. t? acid having a molecular weight between about i w g z g of "cord in the 170 and 350.

2. A liquid composition for depositing a cor- 5 UNZTED STATES PA'I'EN'IB rosion inhibiting film upon metal surfaces conm um 1 sisting essentially of an unctuous solvent and from 3 165.515 Schmidt July 11 1939 about 0.5 to about 5% by weight, based on the {333,206 Sloan Nov 1943 solvent, oi a corrosion inhibiting salt or s dehy- 31385013 i"""""'' 1944 drogenated rosin amine and stearic acid. 10 2 2: 99 Duncan 14: 1945 2,401.02: wmn June 11, 1946 EDWARD 2,412,208 mm- Dec. 11, 1946 

